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  Process to produce low viscosity poly-alpha-olefinsUSPTO Application #: 20070043248Title: Process to produce low viscosity poly-alpha-olefins Abstract: This invention relates to a process to produce a polyalpha-olefin comprising: 1) contacting one or more alpha-olefin monomers having 3 to 24 carbon atoms with an unbridged substituted bis cyclopentadienyl transition metal compound having: 1) at least one non-isoolefin substitution on both cyclopentadientyl rings, or 2) at least two substitutions on at least one cyclopentadienyl ring, a non-coordinating anion activator, and optionally an alkyl-aluminum compound, where the molar ratio of transition metal compound to activator is 10:1 to 0.1:1, and if the alkyl aluminum compound is present then the molar ratio of alkyl aluminum compound to transition metal compound is 1:4 to 4000:1, under polymerization conditions wherein: i) hydrogen is present at a partial pressure of 0.1 to 50 psi, based upon the total pressure of the reactor or the concentration of the hydrogen is from 1 to 10,000 ppm or less by weight; ii) wherein the alpha-olefin monomer(s) having 3 to 24 carbon atoms are present at 10 volume % or more based upon the total volume of the catalyst/activator/alkylaluminum compound solutions, monomers, and any diluents or solvents present in the reaction; iii) the residence time of the reaction is at least 5 minutes; iv) the productivity of the process is at least 43,000 grams of total product per gram of transition metal compound; v) the process is continuous or semi-continuous, and vi) the temperature in the reaction zone does not rise by more than 10° C. during the reaction; and vii) ethylene is not present at more than 30 volume % of the monomers entering the reaction zone; and 2) obtaining a polyalpha-olefin (PAO), optionally hydrogenating the PAO, wherein the PAO comprises at least 50 mole % of a C3 to C24 alpha-olefin monomer, and wherein the PAO has a kinematic viscosity at 100° C. of 20 cSt or less. (end of abstract) Agent: Exxonmobil Chemical Company - Baytown, TX, US Inventors: Margaret May-som Wu, Catalina L. Coker, John F. Walzer, Peijun Jiang USPTO Applicaton #: 20070043248 - Class: 585521000 (USPTO) Related Patent Categories: Chemistry Of Hydrocarbon Compounds, Unsaturated Compound Synthesis, By Addition Of Entire Unsaturated Molecules, E.g., Polymerization, Etc., Using Extraneous Nonhydrocarbon Agent, E.g., Catalyst, Etc., Hydride Or Organic Compound Or Complex Containing Alkaline-, B-, Or Zn Group Material The Patent Description & Claims data below is from USPTO Patent Application 20070043248. Brief Patent Description - Full Patent Description - Patent Application Claims
PRIORITY CLAIM [0001] This invention claims the benefit of U.S. Ser. No. 60/700,600, filed Jul. 19, 2005. FIELD OF THE INVENTION [0002] This invention relates to a process to produce poly-alpha-olefins (PAOs) in the presence of a metallocene catalyst with a non-coordinating anion activator and hydrogen. DESCRIPTION OF RELATED ART [0003] Efforts to improve upon the performance of natural mineral oil-based lubricants by the synthesis of oligomeric hydrocarbon fluids have been the subject of important research and development in the petroleum industry for at least fifty years. These efforts have led to the relatively recent market introduction of a number of synthetic lubricants. In terms of lubricant property improvement, the thrust of the industrial research efforts involving synthetic lubricants have been towards fluids exhibiting useful viscosities over a wide temperature range, i.e., improved viscosity index (VI), while also showing lubricities, thermal and oxidative stabilities and pour points equal to or better than those for mineral oil. [0004] The viscosity-temperature relationship of a lubricating oil is one of the critical criteria which must be considered when selecting a lubricant for a particular application. The mineral oils commonly used as a base for single and multigrade lubricants exhibit a relatively large change in viscosity with a change in temperature. Fluids exhibiting such a relatively large change in viscosity with temperature are said to have a low viscosity index. Viscosity index is an empirical number which indicates the rate of change in the viscosity of an oil within a given temperature range. A high VI oil, for example, will thin out at elevated temperatures more slowly than a low VI oil. Usually, a high VI oil is more desirable because it has higher viscosity at higher temperature, which translates into better lubrication and better protection of the contacting machine elements, preferably at high temperatures and or at temperatures over a wide range. VI is calculated according to ASTM method D 2270. [0005] PAOs comprise a class of hydrocarbons manufactured by the catalytic oligomerization (polymerization to low-molecular-weight products) of linear .alpha.-olefin (LAO) monomers. These typically range from 1-octene to 1-dodecene, with 1-decene being a preferred material, although oligomeric copolymers of lower olefins such as ethylene and propylene may also be used, including copolymers of ethylene with higher olefins as described in U.S. Pat. No. 4,956,122 and the patents referred to therein. PAO products have achieved importance in the lubricating oil market. Typically there are two classes of synthetic hydrocarbon fluids (SHF) produced from linear alpha-olefins, the two classes of SHF being denoted as PAO and HVI-PAO (high viscosity index PAO's). PAO's and HVI-PAO's of different viscosity grades are typically produced using promoted BF.sub.3 or AlCl.sub.3 catalysts. [0006] Specifically, PAOs may be produced by the polymerization of olefin feed in the presence of a catalyst such as AlCl.sub.3, BF.sub.3, or BF.sub.3 complexes. Processes for the production of PAOs are disclosed, for example, in the following patents: U.S. Pat. Nos. 3,149,178; 3,382,291; 3,742,082; 3,769,363; 3,780,128; 4,172,855 and 4,956,122, which are fully incorporated by reference. PAOs are also discussed in: Will, J. G. Lubrication Fundamentals, Marcel Dekker: New York, 1980. Subsequent to polymerization, the PAO lubricant range products are typically hydrogenated in order to reduce the residual unsaturation, generally to a level of greater than 90%. HVI-PAO's may also be conveniently made by the polymerization of an alpha-olefin in the presence of a polymerization catalyst such as Friedel-Crafts catalysts. These include, for example, aluminum trichloride, boron trifluoride, aluminum trichloride or boron trifluoride promoted with water, with alcohols such as ethanol, propanol, or butanol, with carboxylic acids, or with esters such as ethyl acetate or ethyl propionate or ether such as diethyl ether, diisopropyl ether, etc. (See for example, the methods disclosed by U.S. Pat. No. 4,149,178 or 3,382,291.) Other descriptions of PAO synthesis are found in the following U.S. patents: U.S. Pat. No. 3,742,082 (Brennan); U.S. Pat. No. 3,769,363 (Brennan); U.S. Pat. No. 3,876,720 (Heilman); U.S. Pat. No. 4,239,930 (Allphin); U.S. Pat. No. 4,367,352 (Watts); U.S. Pat. No. 4,413,156 (Watts); U.S. Pat. No. 4,434,408 (Larkin); U.S. Pat. No. 4,910,355 (Shubkin); U.S. Pat. No. 4,956,122 (Watts); and U.S. Pat. No. 5,068,487 (Theriot). [0007] Another class of HVI-PAOs may be prepared by the action of a supported, reduced chromium catalyst with an alpha-olefin monomer. Such PAOs are described in U.S. Pat. No. 4,827,073 (Wu); U.S. Pat. No. 4,827,064 (Wu); U.S. Pat. No. 4,967,032 (Ho et al.); U.S. Pat. No. 4,926,004 (Pelrine et al.); and U.S. Pat. No. 4,914,254 (Pelrine). Commercially available PAOs include SpectraSyn.TM. 2, 4, 5, 6, 8, 10, 40, 100 and SpectraSyn Ultra.TM. 150, SpectraSyn Ultra.TM. 300, SpectraSyn Ultra.TM. 1000, etc. (ExxonMobil Chemical Company, Houston Tex.). [0008] Synthetic PAOs have found wide acceptability and commercial success in the lubricant field for their superiority to mineral based lubricants. In terms of lubricant property improvement, industrial research efforts on synthetic lubricants have led to PAO fluids exhibiting useful viscosities over a wide range of temperature, i.e., improved viscosity index, while also showing lubricity, thermal and oxidative stability and pour point equal to or better than mineral oil. These relatively new synthetic lubricants lower mechanical friction, enhancing mechanical efficiency over the full spectrum of mechanical loads and do so over a wider range of operating conditions than mineral oil lubricants. [0009] Performance requirements of lubricants are becoming increasingly stringent. New PAOs with improved properties, such as high viscosity index (VI), low pour point, reduced volatility, high shear stability, improved wear performance, increased thermal and oxidative stability, and or wider viscosity range, are needed to meet new performance requirements for lubricants. New methods to provide such new PAOs with improved properties are also needed. [0010] Efforts have been made to prepare various PAOs using metallocene catalyst systems. Examples include U.S. Pat. No. 6,706,828 (equivalent to US 2004/0147693), where PAOs are produced from meso-forms of certain metallocene catalysts under high hydrogen pressure with methyl alumoxane as a activator. Comparative example D of U.S. Pat. No. 6,706,828, however, uses rac-dimethylsilylbis(2-methyl-indenyl)zirconium dichloride in combination with methylalumoxane (MAO) at 100.degree. C. in the presence of hydrogen to produce polydecene. Likewise, WO 02/14384 discloses, among other things, in examples J and K the use of rac-ethyl-bis(indenyl)zirconium dichloride or rac-dimethylsilyl-bis( 2-methyl-indenyl) zirconium dichloride in combination with MAO at 40.degree. C. (at 200 psi hydrogen or 1 mole of hydrogen) to produce isotactic polydecene reportedly having a Tg of -73.8.degree. C., a KV.sub.100 of 702 cSt, and a VI of 296; or to produce polydecene reportedly having a Tg of -66.degree. C., a KV.sub.100 of 1624, and a VI of 341, respectively. Further WO 99/67347 discloses in example 1 the use of ethylidene bis(tetrahydroindenyl)zirconium dichloride in combination with MAO at 50.degree. C. to produce a polydecene having an Mn of 11,400 and 94% vinylidene double bond content. [0011] Others have made various PAOs, such as polydecene, using various metallocene catalysts not typically known to produce polymers or oligomers with any specific tacticity. Examples include WO 96/23751, EP 0 613 873, U.S. Pat. No. 5,688,887, U.S. Pat. No. 6,043,401, WO 03/020856 (equivalent to US 2003/0055184), U.S. Pat. No. 5,087,788, U.S. Pat. No. 6,414,090, U.S. Pat. No. 6,414,091, U.S. Pat. No. 4,704,491, U.S. Pat. No. 6,133,209, and U.S. Pat. No. 6,713,438. [0012] To date however, PAO's made with metallocenes have not found wide applicability in the marketplace, particularly the lubricant marketplace, due to inefficient process, cost and property deficits. The instant invention address such and other needs by providing new PAO's having excellent property combinations and an improved process to produce them. [0013] U.S. Pat. No. 6,548,724 (equivalent to US 2001/0041817 and U.S. Pat. No. 6,548,723) disclose production of oligomer oils using certain metallocene catalysts, typically in combination with methyl alumoxane. Column, 20, line 40 to 44 of U.S. Pat. No. 6,548,724 indicates that Examples, 10-11 indicate that di, tri or tetra substitutions on the cyclopentadienyl rings of the metallocenes are useful for production of high viscosity polyalphaolefins, (viscosities it he range of 20 to 5000 cSt at 100.degree. C.) with improved yields whereas penta alkyl substituted cyclopentadienyl rings are poor." [0014] PCT/US06/21231 filed Jun. 2, 2006 claiming the benefit of U.S. Ser. No. 60/700,600, filed Jul. 19, 2005 describes the production of liquids from monomers having 5 to 24 carbon atoms using racemic metallocenes and non-coordinating anion activators. [0015] Other references of interest include: EP0284708, U.S. Pat. No. 5,846,896, U.S. Pat. No. 5,679,812, EP0321852, U.S. Pat. No. 4,962,262 EP0513380, US2004/0230016, and U.S. Pat. No. 6,642,169. SUMMARY OF INVENTION [0016] This invention relates to a process to produce a polyalpha-olefin comprising: [0017] 1) contacting one or more alpha-olefin monomers having 3 to 24 carbon atoms with an unbridged substituted bis cyclopentadienyl transition metal compound having: 1) at least one non-isoolefin substitution on each cyclopentadienyl ring, or 2) at least two substitutions on at least one cyclopentadienyl ring, preferably having at least two substitutions on each cyclopentadienyl ring, a non-coordinating anion activator, and optionally an alkyl-aluminum compound, where the molar ratio of transition metal compound to activator is 10:1 to 0.1:1, and if the alkyl aluminum compound is present then the molar ratio of alkyl aluminum compound to transition metal compound is 1:4 to 4000:1, under polymerization conditions wherein: [0018] i) hydrogen is present at a partial pressure of 1 to 50 psi or a hydrogen concentration of 10 to 10,000 ppm, based upon the total pressure of the reactor; [0019] ii) wherein the alpha-olefin monomer(s) having 3 to 24 carbon atoms are present at 10 volume % or more based upon the total volume of the catalyst/activator/alkylaluminum compound solutions, monomers, and any diluents or solvents present in the reaction; [0020] iii) the residence time of the reaction is at least 5 minutes; Continue reading... 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